Hello All! My trusty Ford 655A backhoe has been giving me some trouble lately, and it seems to be getting worse. It will run fine for a while, especially when cold, and then eventually will sputter out and die like its running out of fuel. After some time it will generally start up again and run for a while, but will eventually die again. At times it won't restart, unless I pump the primer on the lift pump, in which case it will fire right off and run good for a while, but then it will eventually die again. After I pump the primer for 10 or 15 seconds, I will hear the return start trickling back into the tank, at which point it always starts and runs good - for a while. I have just changed the fuel filter (I thought for sure was the culprit) with no change in the situation. I also drained off the unit next to the filter which I assume is a water drop out, it had no water in it. I thought maybe the lift pump was going bad? It pumps well manually however, Any Ideas? Your help is much appreciated, thanks! Mike
Here's my method for diagnosing fuel starvation issues by using the lift pump (assuming you have diaphragm/lever pump). When you move that lever you're pulling the diaphragm back against spring pressure, release it and the spring pumps the fuel out, until the fuel pressure builds and holds the diaphragm back so there is no pressure on the lever because the spring is held back also (or there is pressure on half the stroke because the spring only pushed some of the fuel out). There is more pressure on the lever when the inlet is plugged and the lever/diaphragm is pulling against a vacuum. You can tell if the pump is pumping air and not full of fuel because it will have normal pressure pushing the lever, but it will spring back with the same pressure, no fuel to dampen the spring pressure. If you can make sense of this it will tell you whether to look upstream or downstream of the lift pump for a blockage. Or you could run the lift pump off a temporary tank to see if it eliminates the problem, but then you'll still have to dig in if you want to fix the original tank and lines.
Here's MY METHOD ...lol.. The lift pump costs about 40.00.. change it.. its been working for 30 years.. lol.. give it a break.. IF it doesn't fix your problem.. hey.. you eliminated 1 of them.. Could be the inj. pump.. BUT.. until you eliminate the feed issue.. we wont know for sure..
The old Fords are terrible about the needle valve in the bottom of the fuel tank stops up easily. take the line off there and see if fuel pours freely, if it doesn't, blow through it back into the tank. If you keep having trouble,consider replacing it with a 1/4 turn valve.
After conducting the tests Delmer described, I believe the issue lies in the fuel supply before the lift pump. That Needle valve sounds liek a good place to start - something tells me Mitch is on to something. Pump guy, I have to say, that even though my generation is mostly comprised of the replace parts till its fixed type, I side with my mentors and fix things by diagnosing them as opposed to throwing parts at something until its fixed. My lift pump is working fine, It's just not getting supply. THanks for your help guys I'll let you know how it goes